Adjusting total body iron for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project

• Published in: The American journal of clinical nutrition 2017-07, Vol.106 (Suppl 1), p.383S-389S
• Main Authors: Mei, Zuguo, Namaste, Sorrel ML, Serdula, Mary, Suchdev, Parminder S, Rohner, Fabian, Flores-Ayala, Rafael, Addo, O Yaw, Raiten, Daniel J
• Format: Article
• Language: English
• Subjects: acute-phase proteins; Adolescent; Adult; Age; Anemia; Anemia - blood; Anemia, Iron-Deficiency - blood; Biomarkers; Biomarkers - analysis; C-reactive protein; C-Reactive Protein - analysis; Child, Preschool; Children; Cross-Sectional Studies; Data processing; False Negative Reactions; Female; Ferrites; Ferritin; Ferritins - blood; Glycoproteins; Humans; Infant; Inflammation; Iron; Iron - analysis; Iron Deficiencies; iron deficiency; Malaria; Median (statistics); Middle Aged; Nutrient deficiency; Nutritional Status; Orosomucoid - analysis; Polls & surveys; Preschool children; preschool-age children; Receptors, Transferrin - blood; Reference Values; Regression analysis; soluble transferrin receptor; Statistical analysis; Supplement—Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA); total body iron; Transferrin; Transferrins; Vector-borne diseases; Women; women of reproductive age; α-1-acid glycoprotein
• ISSN: 0002-9165; 1938-3207
• DOI: 10.3945/ajcn.116.142307

Total body iron (TBI) that is calculated from ferritin and soluble transferrin receptor (sTfR) allows for the evaluation of the full range of iron status from deficiency to excess. However, both ferritin and sTfR are affected by inflammation and malaria, which may require a statistical adjustment. TBI has been used to assess iron status in the United States, but its use worldwide and in settings with inflammation has been limited. We examine whether inflammation-adjusted ferritin and sTfR concentrations affect TBI values and the prevalence of low TBI (5 mg/L or α-1-acid glycoprotein concentration >1 g/L), 2) the application of arithmetic correction factors, and 3) the use of regression correction. Regardless of the method that was used to adjust ferritin and sTfR for inflammation, the adjusted mean TBI decreased in both PSC and WRA compared with unadjusted values. Subsequently, inflammation-adjusted TBI increased the prevalence of low TBI by a median of 4–14 percentage points (pps) in PSC and 1–3 pps in WRA compared with unadjusted TBI. The regression approach resulted in a greater median increase than was achieved with the exclusion or correction-factor approaches, and accounting for malaria in addition to inflammation did not have an added effect on the prevalence estimates. The prevalence of low TBI is underestimated if it is not adjusted by inflammation, particularly in children living in areas with a high prevalence of inflammation.